The present invention relates to reactive foils. More particularly, the present invention relates to a packaged reactive foil assembly.
Reactive foils are used for joining various materials for example, metals, semiconductors, ceramics, plastics, polymer composites and the like. Reactive foils are used very efficiently in joining similar types of materials or dissimilar types of materials. A non-exhaustive list of applications of reactive foil includes among others, the mounting of a heat sink on a chipset, the mounting of radio frequency (RF) connectors on printed circuit boards, attaching ceramic armors to tanks, the mounting of sputtering targets, hermetically sealing of photocells, capacitors, sensors, electronic devices, and the like.
Conventionally, for joining two materials, a reactive foil is placed between the two materials. The reactive foil is then ignited, initiating an exothermic reaction of multiple nanolayers present in the reactive foil. Very high amounts of energy per unit volume are produced by this reaction within fractions of a second, melting the reactive foil. The released energy may also melt a portion of the surface of the materials, creating a strong, true metallic joint. More specifically, reactive foils are multilayered structures and may be used in the creation of strong and permanent bonds between two or more surfaces. Such reactive foils comprise a stack of nanolayers (having thicknesses of the order of nanometers) of two or more elements or compounds, the layers being positioned in alternate configuration. The reactive foils are fabricated by depositing thousands of alternate nanolayers of at least two elements or compounds.
An example of a reactive foil is a multilayered structure comprising multiple nanolayers of aluminum and nickel. Thousands of nanolayers of aluminum and nickel are deposited alternately to form the reactive foil. When the reactive foil is ignited with an energy pulse, the nanolayers of aluminum and nickel start to undergo an exothermic reaction. The exothermic reaction of aluminum and nickel releases high amounts of heat energy per unit volume within fractions of a second. Further, once the reactive foil is ignited, the exothermic reaction is self-propagating and self-sustaining. The reactive foil delivers enough heat energy that is sufficient for melting the whole reactive foil within a fraction of a second. During the exothermic reaction, the temperature of the reactive region may reach a temperature of up to 1500° C. When the reaction is initiated, heat energy flows in a predictable and controllable manner. By varying the composition of the reactive foil, the thickness and number of nanolayers, the temperature, total energy released, and the velocity of energy flow during the exothermic can be controlled.
Controlled and localized heat generated from the reactive foil can be configured to deliver broad ranges of temperatures, heat energy, and energy flow in desired direction(s) and at desired location(s) in any environment. Overall, reactive foil is a promising technology for precise delivery of heat energy. However, this technology is plagued by various drawbacks as described below.
For example, while joining two materials, the reactive foil is placed between the surfaces of two materials. The reactive foil is placed nearly at the desired location of the joint creation between the surfaces. Pressure is applied to the surfaces to prevent any undesired movement of the reactive foil from the desired location of the joint creation. However, in these conventional methods, the reactive foil may get displaced from the original location, thereby creating a malformed or even a faulty joint. Therefore, there exists a need to provide a system and a method for the prevention of the undesirable displacement of the reactive foil.
Further, the exothermic reaction is initiated by providing an energy pulse using means such as the compression of the reactive foil between two surfaces, an electrical pulse, a spark, a hot filament, and a laser beam. However, none of these listed means is simple, reliable, easy to use, cheap, and user friendly. Therefore, there exists a need for a system and a method for providing a simple, reliable, easy to use, cheap, and user friendly means of igniting the reactive foil.
Furthermore, in some cases as the reactive foil melts, the molten material may splatter onto adjacent regions. Splattering of molten material to the adjacent regions leads to the damage of adjacent electronic components, such as capacitors, transistors, resistors, diodes, integrated circuits, and the like. Therefore, there exists a need to provide a system and a method for the protection of adjacent electronic components from the splattering of molten material.
Further, a reactive foil may be used for the joining of two surfaces, wherein the location of the joint is difficult to access and the joining area is very small. Since the area of the joint is small and inaccessible, the use of a smaller reactive foil poses a problem in terms of the precise handling placement of the reactive foil at the desired location of the joint creation. Therefore, there exists a need for a system and a method to facilitate the joining of small and inaccessible areas.
It is therefore desirable to provide a system and a method to address the issues of the undesired displacement of the reactive foil, ignition of the reactive foil, splattering of melt material from the reactive foil, and handling and placement of the reactive foil at a location that is very small and inaccessible.